The use of clinch joints to secure a first workpiece to a second workpiece is becoming widespread. For example, clinch joints are commonly used to secure two pieces of sheet metal together. A typical clinching station includes a punch and die assembly including a punch and a die mounted opposite each other for movement relative to each other. The two sheet metal pieces to be clinched are placed in overlapping engagement between the punch and the die. A fluid powered cylinder drives the punch into the workpieces, deforming the workpieces into interlocking engagement with each other.
A clinching station may also be used to clinch a nut or a bolt to a piece of sheet metal. The resulting part is a piece of sheet metal having either a nut or a bolt secured thereto. The sheet metal is then used to build a desired product, with the secured nut or bolt facilitating assembly of the end product.
Although existing clinching stations and clinching methods have been commercially successful, sometimes, the formed clinch joints are defective. For example, if the parts to be clinched do not overlap at the location of punch impact, the punch will only deform one of the parts and fail to form an effective clinch joint. An other potential problem associated with existing clinching stations is a possibility that more than two parts are located in the region of punch impact.
In particular, when securing nuts to a piece of sheet metal, sometimes the nutfeeder may inadvertently place two nuts at the punch. When the punch is driven toward the die, the presence of the two nuts instead of one results in a defective clinching operation. Further, sometimes the nutfeeder may fail to place a nut at the punch, resulting in a defective clinching operation.